Submission #398499

#	Time	Username	Problem	Language	Result	Execution time	Memory
398499		MarcoMeijer	Cat (info1cup19_cat)	C++14	100 / 100	527 ms	14692 KiB

cat

#include <bits/stdc++.h>
using namespace std;
 
// macros
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ll, ll> lll;
typedef tuple<int, int, int> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<iii> viii;
typedef vector<ll> vll;
typedef vector<lll> vlll;
#define REP(a,b,c) for(int a=int(b); a<int(c); a++)
#define RE(a,c) REP(a,0,c)
#define RE1(a,c) REP(a,1,c+1)
#define REI(a,b,c) REP(a,b,c+1)
#define REV(a,b,c) for(int a=int(c-1); a>=int(b); a--)
#define FOR(a,b) for(auto& a : b)
#define all(a) a.begin(), a.end()
#define INF 1e18
#define EPS 1e-9
#define pb push_back
#define popb pop_back
#define fi first
#define se second
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
 
// input
template<class T> void IN(T& x) {cin >> x;}
template<class H, class... T> void IN(H& h, T&... t) {IN(h); IN(t...); }
 
// output
template<class T1, class T2> void OUT(const pair<T1,T2>& x);
template<class T> void OUT(const vector<T>& x);
template<class T> void OUT(const T& x) {cout << x;}
template<class H, class... T> void OUT(const H& h, const T&... t) {OUT(h); OUT(t...); }
template<class T1, class T2> void OUT(const pair<T1,T2>& x) {OUT(x.fi,' ',x.se);}
template<class T> void OUT(const vector<T>& x) {RE(i,x.size()) OUT(i==0?"":" ",x[i]);}
template<class... T> void OUTL(const T&... t) {OUT(t..., "\n"); }
template<class H> void OUTLS(const H& h) {OUTL(h); }
template<class H, class... T> void OUTLS(const H& h, const T&... t) {OUT(h,' '); OUTLS(t...); }
 
// dp
template<class T> bool ckmin(T&a, T&b) { bool bl = a > b; a = min(a,b); return bl;}
template<class T> bool ckmax(T&a, T&b) { bool bl = a < b; a = max(a,b); return bl;}
 
void program();
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    program();
}
 
 
//===================//
//   begin program   //
//===================//
 
const int MX = 5e5;
const int N = (1<<20);

int testCases;
int n, a[MX], ra[MX];

void program() {
    IN(testCases);
    while(testCases--) {
        IN(n);
        RE1(i,n) IN( a[i]);
        RE1(i,n) ra[a[i]] = i;;

        // keeping track of the swaps
        vii ans;
        auto makeSwap = [&](int x, int y) {
            swap(a[x],a[y]);
            swap(a[n-x+1], a[n-y+1]);
            ra[a[x]] = x;
            ra[a[y]] = y;
            ra[a[n-x+1]] = n-x+1;
            ra[a[n-y+1]] = n-y+1;
            ans.pb({x,y});
        };

        RE1(i,n/2) if(ra[i] != i && ra[i] != n-i+1) {
            makeSwap(i,ra[i]);
        }
        
        vi wrongSide;
        RE1(i,n/2) if(a[i] > n/2) wrongSide.pb(i);
        
        // check if it is possible
        bool possible = true;
        RE1(i,n) if(a[i] + a[n-i+1] != n+1) possible = false;
        if(wrongSide.size()%2) possible = false;
        if(!possible) {
            OUTL(-1);
            continue;
        }

        RE(i,wrongSide.size()) {
            makeSwap(wrongSide[i], wrongSide[i+1]);
            makeSwap(wrongSide[i], n-wrongSide[i+1]+1);
            i++;
        }

        OUTLS(ans.size(),ans.size());
        FOR(p,ans) OUTL(p);
    }
}

• Subtask 1: 15 / 15
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 15 / 15
• Subtask 5: 35 / 35